Burners used in electric furnaces for melting steel scrap or in melting furnaces for copper, require a fuel which has similar properties to that of a liquid fuel such as a heavy oil. These similarities to a liquid fuel include a fuel that generates a flame having a temperature of not less than 2,000.degree. C., and a fuel that produces a stable flame which is not extinguished in spite of an atmospheric temperature of about several hundred Celsius degree.
Although pulverized coal costs less than liquid fuel, it is quite difficult to expect the pulverized coal to have the above-mentioned similar property since its combustion rate is extremely slow. Therefore, as disclosed in Japanese Published Unexamined patent application No. 59-115904, upon the employment of the pulverized coal as fuel for the burner, there has been applied a mixed combustion process in which the pulverized coal is, instead of being burned by itself, burned along with a liquid or gaseous fuel. According to this mixed combustion process, it is possible to produce a flame having a relatively high temperature and also to reduce the fuel cost sO that it is more economical than a monofuel combustion process in which the liquid fuel is burned singly.
However, in the mixed combustion process, there must anyway be used liquid fuel or gaseous fuel. Furthermore, the mixture ratio of the liquid or gaseous fuel, upon the charging of the cold charge (such as steel scrap, aluminum and copper etc.) into the furnace, must be severely increased in order to prevent the flame from extinguishing due to the decrease of the furnace wall-radiated radiant heat in the vicinity of the burner. In other words, the consumption of pulverized coal in accordance with the mixed combustion process is extremely low in contrast to consumption in accordance with the monofuel combustion process, meaning pulverized coal has not been effectively utilized as an economical fuel which can lower energy cost.
The present invention is proposed regarding the above-mentioned situation. An object of the present invention is to provide a process for burning pulverized coal according to which the monofuel combustion of the pulverized coal produces a stable flame having a high temperature of not less than 2,000.degree. C. even though the atmospheric temperature is approximately room temperature.
Another object of the present invention is to provide a process for burning pulverized coal which substantially decreases the fuel expense of burners for melting metals.